1. Field
This invention relates generally to the disposal of highly radioactive components, and, more particularly, to a method for reducing the volume of radioactive rectangular tubular fuel channels for storage.
2. Related Art
One type of commonly used boiling water nuclear reactor employs a nuclear fuel assembly comprised of fuel rods surrounded by a fuel channel. The fuel channel is a 5.3 inch (13.4 cm) square tube having rounded corners, approximately 14 feet long, with open ends. The channels are typically made of zircoloy and have a wall thickness of 0.08, 0.10 or 0.12 inch (0.2, 0.25 or 0.3 cm).
There are a large number of fuel assemblies in a boiling water reactor, and approximately one-third of these assemblies are normally replaced each year. Even though the fuel channels are normally reused after the fuel rods are removed, for various reasons, they need to replaced from time to time, thereby requiring these highly radioactive fuel channels to be disposed of safely.
Following functional service, irradiated fuel channels are difficult to store and dispose of because of their size, configuration, embrittled condition and radiological history. These used fuel channels are highly radioactive for two reasons. First, the zircoloy metal itself becomes radioactive during operation in the nuclear reactor. Secondly, a crust or crud forms on the outside of the fuel channels which is also radioactive. Heretofore, in the United States, the irradiated fuel channels have been stored in spent fuel pools at the nuclear plants in which they experienced service. This type of storage is extremely space inefficient, but dry-cask storage is not readily available. Accordingly, boiling water reactor operators would prefer to dispose of the fuel channels offsite as soon as reasonably practicable.
Fuel channels and other irradiate hardware are typically classified as class C low level radioactive waste, as defined and determined pursuant to 10 CFR 61 and related regulatory guidance. Since Jul. 1, 2008 low level radioactive waste generators within the United States that are located outside of the Atlantic compact (i.e., Connecticut, New Jersey and South Carolina) have not had access to offsite class B or class C low level radioactive waste disposal capacity. A lack of offsite disposal capacity has caused boiling water reactor operators considerable spent fuel pool overcrowding. Though currently very uncertain and subject to numerous regulatory and commercial challenges, class B and C low level radioactive waste disposal capacity for the remainder of the United States low level radioactive waste generators is anticipated in the near future.
In order for the fuel channels to be shipped for offsite storage an economical method of packaging the fuel channels will be required for such offsite storage to be efficient and cost effective. For that to practically occur, the volume of the fuel channels will have to be significantly reduced. One prior art method for the volume reduction of fuel channels that has been employed is the imprecise crushing and shearing of segments of the fuel channel directly above an open disposal liner placed in the bottom of the spent fuel pool into which the crushed and sheared sections fall. Other methods which have been suggested are described in U.S. Pat. Nos. 4,295,401, 4,507,840 and 5,055,236.
For the general purposes of this description, the principal component of a boiling water reactor fuel channel is a metallic generally square, elongated tube the approximate length of a fuel assembly. Following the useful life of a fuel channel, its primary metal constituents are embrittled as a result of prolonged neutron exposure. Segmentation of the fuel channel causes the embrittled metal to shatter thereby exposing the spent fuel pool to unwanted and highly radioactive debris. Furthermore, packaging for disposal requires size reduction of the fuel channels to fit within commercially available, licensed shipping casks and/or to efficiently utilize disposal package space. Lateral segmentation of the fuel channels is generally a prerequisite in order to efficiently utilize the shipping casks, and has historically been technically problematic.
Accordingly, a new method is desired that enables lateral segmentation and compaction of the fuel channel components without historic untoward consequences.
More specifically, such a method is desired that will minimize the creation of any collateral radioactive debris.
Further, such a method is desired that can be efficiently performed cost effectively.